Montgomery Township officials have approved a preliminary budget for next year that does not raise property taxes.   The spending plan also continues the Homestead Exemption that allows more than 75% of the residential property owners in the township to shield $30,000 of the assessed value of their home from taxation.   Most of those that work in the township will be paying a higher levy on their wages though.   The preliminary budget replaces the annual $10 Occupational Privledge Tax with the $52 per year Local Services Tax.